Ponente
Descripción
Graphene Quantum Dots (GQD) are stable and highly biocompatible fluorescent materials offering excellent potential applications in biological labeling, LEDs, and photonic and spintronic technologies. Red-emitting GQDs are of particular interest for biomedical applications due to the better tissue penetration of red light. In this work, we examined the influence of type, concentration, and configuration of impurities in the energy gap width of the GQDs. For this purpose, different polyaromatic molecules in the form of a regular hexagon doped with graphitic nitrogen or boron were used as models. The energies and populations of their molecular orbitals were obtained using DFTB+, and compared according to linear dimensions and dopant concentration, paying attention to the energy gap width. It was observed that for an increase in the concentration of both dopant types, the bandgap decreases with a proportionality close to the 1/2 power of the dopant concentration for both nitrogen and boron. That indicates a red shift in the emission and absorption spectra, suggesting that the graphitic configuration of the heteroatoms is highly significant in the photoluminescence mechanism since both the presence of a donor and an acceptor impurity coincide in their effects on the band gap.
